As reported in bug 208445 org.netbeans.freemarker.templates.ScriptingCreateFromTemplateTest.testCreateFromTemplateEncodingProperty is failing on Mac with JDK7u4. Please, evaluate and possibly fix it.
junit.framework.ComparisonFailure: null expected:<[text/x-freemarker]> but was:<[content/unknown]>
at junit.framework.Assert.assertEquals(Assert.java:81)
at junit.framework.Assert.assertEquals(Assert.java:87)
at org.netbeans.freemarker.templates.ScriptingCreateFromTemplateTest.testCreateFromTemplateEncodingProperty(ScriptingCreateFromTemplateTest.java:93)

It looks like this depends on the order of executed tests, I do not think this has anything with Mac's JDK specifically. But it can be that the new JDK alters something that allows the tests to be altered randomly.
Reducing the priority to P3 as it does not seem to be a bug in JDK.
This problem occurs when
ScriptingCreateFromTemplateTest.testFreeFileExtension() is run before
ScriptingCreateFromTemplateTest.testCreateFromTemplateEncodingProperty()
In that case, that the list of MIME resolvers is initialized to an empty array from:
Resolvers assigned with []
org.openide.filesystems.MIMESupport$CachedFileObject.getResolvers(MIMESupport.java:243)
org.openide.filesystems.MIMESupport$CachedFileObject.resolveMIME(MIMESupport.java:376)
org.openide.filesystems.MIMESupport$CachedFileObject.getMIMEType(MIMESupport.java:321)
org.openide.filesystems.MIMESupport.findMIMEType(MIMESupport.java:140)
org.openide.filesystems.FileUtil.getMIMEType(FileUtil.java:1481)
org.openide.filesystems.FileObject.getMIMEType(FileObject.java:587)
org.openide.filesystems.AbstractFileObject.getMIMEType(AbstractFileObject.java:195)
org.openide.loaders.DataLoaderPool.allLoaders(DataLoaderPool.java:332)
org.openide.loaders.DataLoaderPool.findDataObject(DataLoaderPool.java:530)
org.openide.loaders.DataLoaderPool.findDataObject(DataLoaderPool.java:493)
org.openide.loaders.DataObject.find(DataObject.java:528)
org.netbeans.freemarker.templates.ScriptingCreateFromTemplateTest.testFreeFileExtension(ScriptingCreateFromTemplateTest.java:135)
and therefore "text/x-freemarker" is not found at ScriptingCreateFromTemplateTest.testCreateFromTemplateEncodingProperty()

Neither a threading issue nor a JDK-specific issue, just depends on order of test execution and easily reproduced using -Dtest-unit-sys-prop.NbTestCase.order=shuffle (simulates unpredictability native to JDK 7).